Allow tasks to notice if client disconnected

This inserts a callable `waitress.client_disconnected` into the
environment that allows the task to check if the client disconnected
while waiting for the response at strategic points in the execution,
allowing to cancel the operation.

It requires setting the new adjustment `channel_request_lookahead` to a
value larger than 0, which continues to read requests from a channel
even if a request is already being processed on that channel, up to the
given count, since a client disconnect is detected by reading from a
readable socket and receiving an empty result.

1 files changed, 14 insertions, 0 deletions

diff --git a/CHANGES.txt b/CHANGES.txt
index f4d1acc..894ff94 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -1,5 +1,19 @@
 2.0.0 (unreleased)
 ------------------
+- Allow tasks to notice if the client disconnected.
+
+  This inserts a callable `waitress.client_disconnected` into the environment
+  that allows the task to check if the client disconnected while waiting for
+  the response at strategic points in the execution and to cancel the
+  operation.
+
+  It requires setting the new adjustment `channel_request_lookahead` to a value
+  larger than 0, which continues to read requests from a channel even if a
+  request is already being processed on that channel, up to the given count,
+  since a client disconnect is detected by reading from a readable socket and
+  receiving an empty result.
+
+  See https://github.com/Pylons/waitress/pull/310
 
 - Drop Python 2.7 support